Thermoplastic resins exhibit excellent physical properties such as low specific gravity, good moldability and good impact resistance, as compared with glass or metal. With the trend of low cost, larger and lighter weight electric and electronic products, plastic products made of thermoplastic resins are quickly replacing existing glass or metal-based products, thereby broadening applications thereof from electric and electronic products to automobile components. In line with this trend, functions as exterior materials and external appearance are increasingly important. In addition, there is a strong need for resins having good scratch resistance for ensuring stability from exterior shock or scratch or flame retardancy for ensuring stability against fire.
Polycarbonate resins exhibit not only excellent mechanical strength, flame retardancy, transparency and weather resistance, but also good impact resistance, thermal stability. However, the polycarbonate resins have a drawback in that they exhibit very poor scratch resistance.
Acrylic resins, specifically, polymethyl methacrylate (PMMA) resins, have excellent transparency, weather resistance, mechanical strength, surface gloss, adhesion, and, particularly, remarkably excellent scratch resistance. However, the acrylic resins have drawbacks of very poor impact resistance and flame retardancy.
In order to overcome these problems while achieving mechanical properties including impact resistance and scratch resistance, a polymethyl methacrylate (PMMA) resin is prepared by copolymerization of monomers having high indices of refraction, or a polycarbonate (PC)/PMMA resin is prepared by mixing polycarbonate (PC) and acrylic resins, for example, PMMA. In addition, to improve resin compatibility of PC/PMMA, an acrylic copolymer having a high index of refraction is employed to prepare an alloy resin of polycarbonate and acrylic resins having high flame retardancy and scratch resistance. However, the copolymer of the monomers having high indices of refraction has a limit in improvement of refractivity or heat resistance. Moreover, the alloy resin of polycarbonate and acrylic resin exhibit almost no flame retardancy due to a low content of a flame retardant and is likely to suffer from deterioration in mechanical properties including heat resistance when containing a flame retardant.